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<pre><span class="sourceLineNo">001</span><a name="line.1"></a>
<span class="sourceLineNo">002</span>/*<a name="line.2"></a>
<span class="sourceLineNo">003</span> * Copyright (C) 2014 Archie L. Cobbs. All rights reserved.<a name="line.3"></a>
<span class="sourceLineNo">004</span> *<a name="line.4"></a>
<span class="sourceLineNo">005</span> * $Id: NullSafeType.html 743 2015-01-28 21:39:47Z archie.cobbs $<a name="line.5"></a>
<span class="sourceLineNo">006</span> */<a name="line.6"></a>
<span class="sourceLineNo">007</span><a name="line.7"></a>
<span class="sourceLineNo">008</span>package org.jsimpledb.core;<a name="line.8"></a>
<span class="sourceLineNo">009</span><a name="line.9"></a>
<span class="sourceLineNo">010</span>import org.jsimpledb.parse.ParseContext;<a name="line.10"></a>
<span class="sourceLineNo">011</span>import org.jsimpledb.util.ByteReader;<a name="line.11"></a>
<span class="sourceLineNo">012</span>import org.jsimpledb.util.ByteWriter;<a name="line.12"></a>
<span class="sourceLineNo">013</span><a name="line.13"></a>
<span class="sourceLineNo">014</span>/**<a name="line.14"></a>
<span class="sourceLineNo">015</span> * A {@link FieldType} that wraps any other {@link FieldType} not supporting null values and adds support for null values<a name="line.15"></a>
<span class="sourceLineNo">016</span> * by pre-pending to the binary encoding a {@code 0x00} for non-null values or a {@code 0xff} byte for null values. Therefore,<a name="line.16"></a>
<span class="sourceLineNo">017</span> * null values sort last.<a name="line.17"></a>
<span class="sourceLineNo">018</span> *<a name="line.18"></a>
<span class="sourceLineNo">019</span> * &lt;p&gt;<a name="line.19"></a>
<span class="sourceLineNo">020</span> * The default value becomes null, for which {@code "null"} is the value returned by {@link #toParseableString toParseableString()}.<a name="line.20"></a>
<span class="sourceLineNo">021</span> * Therefore, {@code "null"} must not be returned by the wrapped type's {@link #toParseableString toParseableString()}<a name="line.21"></a>
<span class="sourceLineNo">022</span> * for any value.<a name="line.22"></a>
<span class="sourceLineNo">023</span> * &lt;/p&gt;<a name="line.23"></a>
<span class="sourceLineNo">024</span> *<a name="line.24"></a>
<span class="sourceLineNo">025</span> * &lt;p&gt;<a name="line.25"></a>
<span class="sourceLineNo">026</span> * This class will automatically "inline" the {@code 0xff} for null values if the wrapped {@link FieldType}'s<a name="line.26"></a>
<span class="sourceLineNo">027</span> * {@link FieldType#hasPrefix0xff} method returns false.<a name="line.27"></a>
<span class="sourceLineNo">028</span> * &lt;/p&gt;<a name="line.28"></a>
<span class="sourceLineNo">029</span> */<a name="line.29"></a>
<span class="sourceLineNo">030</span>public class NullSafeType&lt;T&gt; extends FieldType&lt;T&gt; {<a name="line.30"></a>
<span class="sourceLineNo">031</span><a name="line.31"></a>
<span class="sourceLineNo">032</span>    /**<a name="line.32"></a>
<span class="sourceLineNo">033</span>     * Not null sentinel byte value. Used only when inlining is not in effect.<a name="line.33"></a>
<span class="sourceLineNo">034</span>     */<a name="line.34"></a>
<span class="sourceLineNo">035</span>    public static final int NOT_NULL_SENTINEL = 0x01;<a name="line.35"></a>
<span class="sourceLineNo">036</span><a name="line.36"></a>
<span class="sourceLineNo">037</span>    /**<a name="line.37"></a>
<span class="sourceLineNo">038</span>     * Null sentinel byte value.<a name="line.38"></a>
<span class="sourceLineNo">039</span>     */<a name="line.39"></a>
<span class="sourceLineNo">040</span>    public static final int NULL_SENTINEL = 0xff;<a name="line.40"></a>
<span class="sourceLineNo">041</span><a name="line.41"></a>
<span class="sourceLineNo">042</span>    private static final byte[] DEFAULT_VALUE = new byte[] { (byte)NULL_SENTINEL };<a name="line.42"></a>
<span class="sourceLineNo">043</span><a name="line.43"></a>
<span class="sourceLineNo">044</span>    /**<a name="line.44"></a>
<span class="sourceLineNo">045</span>     * The inner {@link FieldType} that this instance wraps.<a name="line.45"></a>
<span class="sourceLineNo">046</span>     */<a name="line.46"></a>
<span class="sourceLineNo">047</span>    protected final FieldType&lt;T&gt; inner;<a name="line.47"></a>
<span class="sourceLineNo">048</span><a name="line.48"></a>
<span class="sourceLineNo">049</span>    private final boolean inline;<a name="line.49"></a>
<span class="sourceLineNo">050</span><a name="line.50"></a>
<span class="sourceLineNo">051</span>    /**<a name="line.51"></a>
<span class="sourceLineNo">052</span>     * Constructor.<a name="line.52"></a>
<span class="sourceLineNo">053</span>     *<a name="line.53"></a>
<span class="sourceLineNo">054</span>     * @param name type name<a name="line.54"></a>
<span class="sourceLineNo">055</span>     * @param inner inner type that is not null safe<a name="line.55"></a>
<span class="sourceLineNo">056</span>     */<a name="line.56"></a>
<span class="sourceLineNo">057</span>    public NullSafeType(String name, FieldType&lt;T&gt; inner) {<a name="line.57"></a>
<span class="sourceLineNo">058</span>        super(name, inner.getTypeToken().wrap(), inner.getEncodingSignature());<a name="line.58"></a>
<span class="sourceLineNo">059</span>        if (inner instanceof NullSafeType)<a name="line.59"></a>
<span class="sourceLineNo">060</span>            throw new IllegalArgumentException("inner type is already null-safe");<a name="line.60"></a>
<span class="sourceLineNo">061</span>        this.inner = inner;<a name="line.61"></a>
<span class="sourceLineNo">062</span>        this.inline = !inner.hasPrefix0xff();<a name="line.62"></a>
<span class="sourceLineNo">063</span>    }<a name="line.63"></a>
<span class="sourceLineNo">064</span><a name="line.64"></a>
<span class="sourceLineNo">065</span>    /**<a name="line.65"></a>
<span class="sourceLineNo">066</span>     * Constructor. Takes type name from {@code inner}; therefore, this instance and {@code inner}<a name="line.66"></a>
<span class="sourceLineNo">067</span>     * cannot be both registered in a {@link FieldTypeRegistry}.<a name="line.67"></a>
<span class="sourceLineNo">068</span>     *<a name="line.68"></a>
<span class="sourceLineNo">069</span>     * @param inner inner type that is not null safe<a name="line.69"></a>
<span class="sourceLineNo">070</span>     */<a name="line.70"></a>
<span class="sourceLineNo">071</span>    public NullSafeType(FieldType&lt;T&gt; inner) {<a name="line.71"></a>
<span class="sourceLineNo">072</span>       this(inner.name, inner);<a name="line.72"></a>
<span class="sourceLineNo">073</span>    }<a name="line.73"></a>
<span class="sourceLineNo">074</span><a name="line.74"></a>
<span class="sourceLineNo">075</span>    @Override<a name="line.75"></a>
<span class="sourceLineNo">076</span>    public T read(ByteReader reader) {<a name="line.76"></a>
<span class="sourceLineNo">077</span>        if (this.inline) {<a name="line.77"></a>
<span class="sourceLineNo">078</span>            if (reader.peek() == NULL_SENTINEL) {<a name="line.78"></a>
<span class="sourceLineNo">079</span>                reader.skip(1);<a name="line.79"></a>
<span class="sourceLineNo">080</span>                return null;<a name="line.80"></a>
<span class="sourceLineNo">081</span>            }<a name="line.81"></a>
<span class="sourceLineNo">082</span>            return this.inner.read(reader);<a name="line.82"></a>
<span class="sourceLineNo">083</span>        } else {<a name="line.83"></a>
<span class="sourceLineNo">084</span>            switch (reader.readByte()) {<a name="line.84"></a>
<span class="sourceLineNo">085</span>            case NULL_SENTINEL:<a name="line.85"></a>
<span class="sourceLineNo">086</span>                return null;<a name="line.86"></a>
<span class="sourceLineNo">087</span>            case NOT_NULL_SENTINEL:<a name="line.87"></a>
<span class="sourceLineNo">088</span>                return this.inner.read(reader);<a name="line.88"></a>
<span class="sourceLineNo">089</span>            default:<a name="line.89"></a>
<span class="sourceLineNo">090</span>                throw new IllegalArgumentException("invalid encoding of " + this);<a name="line.90"></a>
<span class="sourceLineNo">091</span>            }<a name="line.91"></a>
<span class="sourceLineNo">092</span>        }<a name="line.92"></a>
<span class="sourceLineNo">093</span>    }<a name="line.93"></a>
<span class="sourceLineNo">094</span><a name="line.94"></a>
<span class="sourceLineNo">095</span>    @Override<a name="line.95"></a>
<span class="sourceLineNo">096</span>    public void write(ByteWriter writer, T value) {<a name="line.96"></a>
<span class="sourceLineNo">097</span>        if (value == null) {<a name="line.97"></a>
<span class="sourceLineNo">098</span>            writer.writeByte(NULL_SENTINEL);<a name="line.98"></a>
<span class="sourceLineNo">099</span>            return;<a name="line.99"></a>
<span class="sourceLineNo">100</span>        }<a name="line.100"></a>
<span class="sourceLineNo">101</span>        if (!this.inline)<a name="line.101"></a>
<span class="sourceLineNo">102</span>            writer.writeByte(NOT_NULL_SENTINEL);<a name="line.102"></a>
<span class="sourceLineNo">103</span>        this.inner.write(writer, value);<a name="line.103"></a>
<span class="sourceLineNo">104</span>    }<a name="line.104"></a>
<span class="sourceLineNo">105</span><a name="line.105"></a>
<span class="sourceLineNo">106</span>    @Override<a name="line.106"></a>
<span class="sourceLineNo">107</span>    public byte[] getDefaultValue() {<a name="line.107"></a>
<span class="sourceLineNo">108</span>        return DEFAULT_VALUE;<a name="line.108"></a>
<span class="sourceLineNo">109</span>    }<a name="line.109"></a>
<span class="sourceLineNo">110</span><a name="line.110"></a>
<span class="sourceLineNo">111</span>    @Override<a name="line.111"></a>
<span class="sourceLineNo">112</span>    public void skip(ByteReader reader) {<a name="line.112"></a>
<span class="sourceLineNo">113</span>        if (this.inline) {<a name="line.113"></a>
<span class="sourceLineNo">114</span>            final int prefix = reader.peek();<a name="line.114"></a>
<span class="sourceLineNo">115</span>            switch (prefix) {<a name="line.115"></a>
<span class="sourceLineNo">116</span>            case NULL_SENTINEL:<a name="line.116"></a>
<span class="sourceLineNo">117</span>                reader.skip(1);<a name="line.117"></a>
<span class="sourceLineNo">118</span>                break;<a name="line.118"></a>
<span class="sourceLineNo">119</span>            default:<a name="line.119"></a>
<span class="sourceLineNo">120</span>                this.inner.skip(reader);<a name="line.120"></a>
<span class="sourceLineNo">121</span>                break;<a name="line.121"></a>
<span class="sourceLineNo">122</span>            }<a name="line.122"></a>
<span class="sourceLineNo">123</span>        } else {<a name="line.123"></a>
<span class="sourceLineNo">124</span>            final int prefix = reader.readByte();<a name="line.124"></a>
<span class="sourceLineNo">125</span>            switch (prefix) {<a name="line.125"></a>
<span class="sourceLineNo">126</span>            case NULL_SENTINEL:<a name="line.126"></a>
<span class="sourceLineNo">127</span>                break;<a name="line.127"></a>
<span class="sourceLineNo">128</span>            case NOT_NULL_SENTINEL:<a name="line.128"></a>
<span class="sourceLineNo">129</span>                this.inner.skip(reader);<a name="line.129"></a>
<span class="sourceLineNo">130</span>                break;<a name="line.130"></a>
<span class="sourceLineNo">131</span>            default:<a name="line.131"></a>
<span class="sourceLineNo">132</span>                throw new IllegalArgumentException("invalid encoding of " + this);<a name="line.132"></a>
<span class="sourceLineNo">133</span>            }<a name="line.133"></a>
<span class="sourceLineNo">134</span>        }<a name="line.134"></a>
<span class="sourceLineNo">135</span>    }<a name="line.135"></a>
<span class="sourceLineNo">136</span><a name="line.136"></a>
<span class="sourceLineNo">137</span>    @Override<a name="line.137"></a>
<span class="sourceLineNo">138</span>    public T fromString(String string) {<a name="line.138"></a>
<span class="sourceLineNo">139</span>        return this.inner.fromString(string);<a name="line.139"></a>
<span class="sourceLineNo">140</span>    }<a name="line.140"></a>
<span class="sourceLineNo">141</span><a name="line.141"></a>
<span class="sourceLineNo">142</span>    @Override<a name="line.142"></a>
<span class="sourceLineNo">143</span>    public String toString(T value) {<a name="line.143"></a>
<span class="sourceLineNo">144</span>        if (value == null)<a name="line.144"></a>
<span class="sourceLineNo">145</span>            throw new IllegalArgumentException("null value");<a name="line.145"></a>
<span class="sourceLineNo">146</span>        return this.inner.toString(value);<a name="line.146"></a>
<span class="sourceLineNo">147</span>    }<a name="line.147"></a>
<span class="sourceLineNo">148</span><a name="line.148"></a>
<span class="sourceLineNo">149</span>    @Override<a name="line.149"></a>
<span class="sourceLineNo">150</span>    public T fromParseableString(ParseContext context) {<a name="line.150"></a>
<span class="sourceLineNo">151</span>        return context.tryPattern("null\\b") != null ? null : this.inner.fromParseableString(context);<a name="line.151"></a>
<span class="sourceLineNo">152</span>    }<a name="line.152"></a>
<span class="sourceLineNo">153</span><a name="line.153"></a>
<span class="sourceLineNo">154</span>    @Override<a name="line.154"></a>
<span class="sourceLineNo">155</span>    public String toParseableString(T value) {<a name="line.155"></a>
<span class="sourceLineNo">156</span>        return value == null ? "null" : this.inner.toParseableString(value);<a name="line.156"></a>
<span class="sourceLineNo">157</span>    }<a name="line.157"></a>
<span class="sourceLineNo">158</span><a name="line.158"></a>
<span class="sourceLineNo">159</span>    @Override<a name="line.159"></a>
<span class="sourceLineNo">160</span>    public int compare(T value1, T value2) {<a name="line.160"></a>
<span class="sourceLineNo">161</span>        if (value1 == null)<a name="line.161"></a>
<span class="sourceLineNo">162</span>            return value2 == null ? 0 : 1;<a name="line.162"></a>
<span class="sourceLineNo">163</span>        if (value2 == null)<a name="line.163"></a>
<span class="sourceLineNo">164</span>            return value1 == null ? 0 : -1;<a name="line.164"></a>
<span class="sourceLineNo">165</span>        return this.inner.compare(value1, value2);<a name="line.165"></a>
<span class="sourceLineNo">166</span>    }<a name="line.166"></a>
<span class="sourceLineNo">167</span><a name="line.167"></a>
<span class="sourceLineNo">168</span>    @Override<a name="line.168"></a>
<span class="sourceLineNo">169</span>    public boolean hasPrefix0xff() {<a name="line.169"></a>
<span class="sourceLineNo">170</span>        return true;<a name="line.170"></a>
<span class="sourceLineNo">171</span>    }<a name="line.171"></a>
<span class="sourceLineNo">172</span><a name="line.172"></a>
<span class="sourceLineNo">173</span>    @Override<a name="line.173"></a>
<span class="sourceLineNo">174</span>    public boolean hasPrefix0x00() {<a name="line.174"></a>
<span class="sourceLineNo">175</span>        return this.inline &amp;&amp; this.inner.hasPrefix0x00();<a name="line.175"></a>
<span class="sourceLineNo">176</span>    }<a name="line.176"></a>
<span class="sourceLineNo">177</span><a name="line.177"></a>
<span class="sourceLineNo">178</span>// Object<a name="line.178"></a>
<span class="sourceLineNo">179</span><a name="line.179"></a>
<span class="sourceLineNo">180</span>    @Override<a name="line.180"></a>
<span class="sourceLineNo">181</span>    public int hashCode() {<a name="line.181"></a>
<span class="sourceLineNo">182</span>        return super.hashCode() ^ this.inner.hashCode();<a name="line.182"></a>
<span class="sourceLineNo">183</span>    }<a name="line.183"></a>
<span class="sourceLineNo">184</span><a name="line.184"></a>
<span class="sourceLineNo">185</span>    @Override<a name="line.185"></a>
<span class="sourceLineNo">186</span>    public boolean equals(Object obj) {<a name="line.186"></a>
<span class="sourceLineNo">187</span>        if (obj == this)<a name="line.187"></a>
<span class="sourceLineNo">188</span>            return true;<a name="line.188"></a>
<span class="sourceLineNo">189</span>        if (!super.equals(obj))<a name="line.189"></a>
<span class="sourceLineNo">190</span>            return false;<a name="line.190"></a>
<span class="sourceLineNo">191</span>        final NullSafeType&lt;?&gt; that = (NullSafeType&lt;?&gt;)obj;<a name="line.191"></a>
<span class="sourceLineNo">192</span>        return this.inner.equals(that.inner);<a name="line.192"></a>
<span class="sourceLineNo">193</span>    }<a name="line.193"></a>
<span class="sourceLineNo">194</span>}<a name="line.194"></a>
<span class="sourceLineNo">195</span><a name="line.195"></a>




























































</pre>
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